In many transmission systems, both the receiver and transmitter include a clock that controls various activities. The clock is typically a crystal oscillator that controls processing-related activities associated with transmitting and receiving data over a channel. Due to minor variations, the receiver's clock and the transmitter's clock are often offset from each other, i.e., the frequency of the clock at the receiver is often different from that at the transmitter.
One problem associated with mismatched clock frequencies is that the receiver may be unable to recover the transmitted signal without errors. For example, a discrete multitone (DMT) transmission system may transmit data over 256 distinct carriers (also referred to as tones) with each carrier being separated by 4.3125 KHz. When the transmitting and receiving clocks are mismatched, the receiver may be unable to accurately decode the data transmitted on the tones. An error correction code may be inserted into the data prior to transmission to combat the problems associated with mismatched clock frequencies. However, when the frequencies of the transmitting and receiving clocks vary significantly, the error correction code may not provide adequate correction capabilities to ensure that the transmitted signal can be recovered without errors.